Contrast media are used in many medical diagnostic and therapeutic imaging procedures. Diagnostically these include X-ray procedures for instance, angiography, venography and urography, CT scanning, magnetic-resonance imaging MRI!, and ultrasonic imaging. Contrast media is used during therapeutic procedures such as angioplastic and other interventional radiologic procedures. Because this contrast material is injected into the patient, it must be sterile and contain a minimum of pyrogens.
Presently, most contrast is provided in sterilized glass bottles, ranging in size from 20 ml to 200 ml. Plastic packages are also available. Non-ionic X-ray contrast media is expensive, on the order of $1/ml. Ionic contrast media costs about $0.10/ml. Non-ion contrast has fewer complications but because of the cost, it is not universally used. MRI contrast costs about $5/ml. All the containers are single use, which means that once a bottle is opened, it should be used for that patient or thrown away, although a multi-use 1,000 ml bottle has been recently approved by the FDA.
A hospital must purchase and stock many concentrations in multiple bottle sizes to provide the right amount of the right concentration for a specific procedure, while minimizing the wastage of contrast remaining in any opened bottles.
This multitude of sizes and concentrations increases costs throughout the contrast supplier chain. Manufacturers need to make many batches with various concentrations, and package each in many sized bottles. They must have inventories; of each on hand to quickly meet the customer's request. Each concentration and size entails an added regulatory burden.
In the hospital, there are additional costs due to the work purchasing the various brands and sizes, storage space is required for stocking, cabinets are required in each procedure room, and time is required to make sure the right numbers of each bottle are kept in each room. Frustration, waste and/or less than optimal studies can occur if this complex logistics chain fails at any point.
To illustrate the problem, consider a manufacturer who makes 5 concentrations of contrast, packages them in bottles of 10, 25, 50, 75, 100, 150 and 200 ml. The manufacturer now has 35 different products to get approval for, schedule production for, maintain sufficient stock of, and finally, ship to his customers.
Presently, most hospitals utilize a standard protocol for a given set of indications. For instance, for a CT scan of the liver, the protocol may call for 130 ml of contrast injected at 3 ml/s. This protocol is used for a wide variety of patient weights and physical conditions. One goal of this standardization is to minimize errors. Another is to decrease the likelihood of having to repeat the procedure, with the problem of additional radiation and contrast dose to the patient.
However, there are costs associated with this method. Many patients may get more contrast than they need for an image to be diagnostic. Overdosing wastes contrast, but there is no way with the present contrast supply and delivery system to remedy this, without stocking many more sizes of bottles and working harder to fill syringes. Other patients may have studies that are less than optimum. They do not receive enough contrast. The contrast that isn't used doesn't cost anything, but there is a much greater chance of having to repeat the whole procedure, with a much greater cost than a few milliliters of contrast. Again, using many bottle sizes and a, cumbersome filling procedure is the only solution presently available.
In angiography, there are not set protocols to the same extent as in CT, because patient size determines vessel size which in turn determines the volume and flow rate needed. This means that a fixed amount of contrast cannot be prepared ahead of time with any confidence that more won't be needed during the procedure or that a significant amount won't remain and be wasted at the end of the procedure. To avoid delays while working on the patient, the technician loads more than the average amount used, with the realization that some is likely to be wasted, and there still is a chance that a delay will occur when more has to be loaded.
Another problem this system addresses is the volume and cost of items which must be disposed of after each patient. To save contrast, several small glass bottles may be opened per patient. One or more plastic syringes, and various tubing arrangements are used. There is a cost to purchase and a cost to dispose of each of these items.
The problems arising from the use of a multiplicity of concentrations and container sizes was addressed in German DE 4121568A1. In this disclosure, it was provided a supply tank of contrast agent which could contain from about 0.1 to as much as 100 liters. The device also included a similar tank that contained a diluent so that the composition of the resulting mixture could be varied to form a variety of concentrations. The abstract in the German patent utilizes a bulk mechanical mixer with sequential flow and so would not seem to provide for the production of continuously variable concentrations. Nor, and importantly, is there any description of means to prevent cross-contamination when the apparatus is used on a plurality of patients.
Machines for mixing IV solutions also do not connect directly to the patient. Generally, the controls require that the operator know which fluid is in which position and that he choose the mixing ratios. In U.S. Pat. No. 4,341,153, medication is diluted and delivered to a syringe. There are no means described for connection to a patient, there is no mixing means and only sequential flows are described.
U.S. Pat. No. 4,610,790 describes in great detail how to make sterile water for diluting medications. Making diluted fluids is mentioned in little detail. U.S. Pat. No. 4,783,273 describes the use of sterilizing filters to assure the sterility of bulk fluids. Concentration monitors are also described. A serious drawback is the use of chemical sterilants.
In none of the references mentioned above is a mechanism described which can be used to sequentially or simultaneously inject contrast into several patients while minimizing the chance of cross-contamination. Nor is there any mention of information integrity or information transfer so that the proper procedures are followed with the diluted medications.